The night before: Rinse lima beans and place them in a shallow baking dish. Sprinkle with baking soda and cover them with water. Let them soak overnight. (or at least 8 hours)
Place the ham bone in the pressure cooker. Add in beans, tomato juice, and onion, and sprinkle with black pepper.
Set your instant pot to manual and 25 minutes. When the instant pot is done cooking, let it do a slow release for 10 minutes, then manually release the remaining pressure before removing the lid.
Remove ham from the bone and chop. Put the ham back in the soup and serve it hot.
Notes
My grandma called this Lima Bean Soup. When my mom makes it, she only uses about 2/3 of the soaked beans, so that is what I did, too. (about 3 cups of them) I prefer more broth in my soup, and the beans do soak up a lot of the liquid. If you like a thicker soup, use all of the beans. We never add salt to this recipe because the ham has plenty.